Sedimentology
Mohammad Shalalvand; Mohammad Adabi; Afshin Zohdi
Abstract
In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of ...
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In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of marl and dolomite. The main diagenetic processes affecting the TalehZangFormation include micritization, various types of porosity, cementation, dolomitization and compaction. Due to the texture and the abundance of unstable skeletal particles (green algae and bivalve), porosity and cementation aremorecommon among the identified processes. Microscopic and geochemical studies have shown that these processes have taken place in eogenesis and early mesogenesis stages in marine, meteoric and shallow burial environments. Evidences indicate that the carbonates of the TalehZangFormation didnot tolerate deep burial after the deposition during diagenesis. Fluids that affected the lower parts of the formation during burial were mainly marine. Moreover, tothetop ofthe sequence in addition to seawater less meteoric fluids have affected the marine carbonates of the Taleh Zang Formation during diagenesis. The high amounts of Sr/Mn (mean27/51) and Sr/Ca (mean 1/61) and also low Mn (mean 27ppm) and Fe (mean 78ppm) values indicate close digenetic system with low water/rock interaction for the carbonate samples of the TalehZangFormation.
Economic Geology
Negar Kaboudmehri; Hossein Kouhestani; Mir Ali asghar Mokhtari; Afshin Zohdi
Abstract
The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the ...
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The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the plant fossils, and shows disseminated, replacement, solution seems, intergranoular cement, framboidal, and vein-veinlet textures. At Toryan, ore horizon has 1 m thickness and approximately 350 m length and contains three zones include the red oxidized zone, the bleached zone and the mineralized reduced zone. Galena, sphalerite, pyrite and arsenopyrite are the main ore minerals at Toryan occurrence. Cerussite and goethite are formed during supergene and wethering processes. Comparison of trace elements and REE patterns of barren red and grey host sandstones and mineralized samples indicate that mineralized samples show lower concentrations of trace elements and REE. Based on tectonic setting, sedimentary environment, host rock, presence of plant fossils, geometry, ore texture and mineralogy and alteration, Toryan occurrence can be classified as sediment-hosted Cu deposits of Redbed type, and is comparable with another Redbed type of Cu and Pb–Zn deposits in the Avaj-Zanjan-Tabriz-Khoy belt.
Stratigraphy and Palaeontology
Manizhe Famarini Bozchalouei; Nasrollah Abbassi; Armin Salsani; Afshin Zohdi
Abstract
Soltanieh Formation comprises seven informal submembers as alternation of dolomites and shales, more than 1110 meters in thickness, was surveyed in the Seyedkandi section, 32 km southwest of Zanjan, northwest Iran. These submembers were subdivided as lower dolomite, lower shale, second dolomite, second ...
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Soltanieh Formation comprises seven informal submembers as alternation of dolomites and shales, more than 1110 meters in thickness, was surveyed in the Seyedkandi section, 32 km southwest of Zanjan, northwest Iran. These submembers were subdivided as lower dolomite, lower shale, second dolomite, second shale, third dolomite, upper shale and upper dolomite, respectively. Based on ichnological data from 109 specimens, 23 ichnogenera and 42 ichnospecies have been recognised. The abundance of trace fossils is very high in the second shale submember, so that 99 specimens were collected from this rock unit. Ichnofossil data from the studied section showsthat the Neoproterozoic-Cambrian boundary is located in the 8 m above the base of second dolomite submember in the studied section, where the first occurrence of Treptichnus pedum was been recorded.
Economic Geology
Ali Rajabzadeh; Hossein Kouhestani; Mir Ali Asghar Mokhtari; Afshin Zohdi
Abstract
In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and ...
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In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and is conformably overlies the Qom Formation limestones. Based on the microscopic studies, these sandstones mainly composed of fine- to coarse-grained clastic fragments including sedimentary and metamorphic rock fragments (45 %), quartz (38 %) and feldspar (17 %). Based on petrographic studies, these sandstones are feldspathic litharenite and litharenite (mainly chertarenite). Based on the main components and major and minor elements geochemical data, the tectonic setting of these sandstones is an active continental margins and foreland basins. These data represent an intermediate to felsic source rock for these sandstones which was affected by the semi-humid to semi-arid climate and a low chemical weathering.
Sedimentology
Afshin Zohdi
Abstract
In this study, for the first time stratigraphy and depositional history of the Routeh Formation have been evaluated in west of Zanjan (Agh-Bolagh section). These deposits with thickness of 102m consist of limestone, dolomitic limestone with the less frequency of thin-bedded calcareous shales. This sedimentary ...
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In this study, for the first time stratigraphy and depositional history of the Routeh Formation have been evaluated in west of Zanjan (Agh-Bolagh section). These deposits with thickness of 102m consist of limestone, dolomitic limestone with the less frequency of thin-bedded calcareous shales. This sedimentary sequence with an unconformity overlies the quartz-bearing sandstones of Doroud Formation and is overlain by a laterite-bauxite horizon below the vermiculate-bearing limestone of Elika Formation. The main components of Routeh Formation contain different kinds of algae, small benthic foraminifera and with a less frequency echinoderm and brachiopod debris. Based on filed and laboratory studied eight sedimentary facies have been distinguished into the Routeh Formation. These facies due to the different types of allochems, texture and fossil content display a shallow-water marine environment during deposition of the Routeh Formation located at Palaeotethys passive southern margin. The absence of re-sedimented deposits like: turbidites, presence of micrite at the most of facies, lack of continues reefal facies and gradual facies change indicate that the Routeh Formation possibly were deposited in a ramp carbonate platform. Due to great diversity and abundance of algae and benthic foraminifera, this carbonate ramp is referred to as an “algae and foram-dominated carbonate ramp system”. Field observations, facies analyses and sequence stratigraphy studied led to the identification of one-third order depositional sequence into the Routeh Formation. This depositional sequence separated by type-1 sequence boundaries at below with quartz-bearing sandstones of Doroud Formation and at the top with laterite-bauxite horizon between Routeh and Elika formations
Sedimentology
S. A. Moallemi; M. A. Salehi; A. Zohdi
Abstract
In this study, the sandstones of the Razak Formation at the Finu and Hanudun outcrops and at Sarkhun Field north of Bandar-Abbas have been investigated by petrography and geochemistry analyses to discriminate provenance for determination of tectonic setting, parent rock and palaeoweathering and for comparison ...
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In this study, the sandstones of the Razak Formation at the Finu and Hanudun outcrops and at Sarkhun Field north of Bandar-Abbas have been investigated by petrography and geochemistry analyses to discriminate provenance for determination of tectonic setting, parent rock and palaeoweathering and for comparison with the Ahwaz Sandstone of Asmari Formation. The Razak Formation mainly consists of marl, sandstone, conglomerate and sandy limestone. The results of geochemical investigation of major and trace elements indicated that the sedimentation of the Razak Formation took place in an active continental margin. Provenance analysis shows that the siliciclastic sediments of the Razak Formation were largely derived from mafic and intermediate igneous, low- to high-grade metamorphic and sedimentary rocks. Chemical weathering indices suggested that their source area underwent a moderate degree of chemical weathering in an arid climate. It seems that the sediments of the Razak Formation are results of erosion from a mixture of ophiolitic-igneous rocks belonging to the Neo-Tethys oceanic crust, metamorphic rocks and other sedimentary strata deposited in Zagros sedimentary basin during foreland basin evolution. Wedge thickness of the Razak Formation changes from the hinterland thrust basin towards the Zagros trough and ridge basin and finally disappears in the coastal Fars region. The presence of polymictic conglomerate and coarse-grained sandstone with abundant rock fragments could be considered as additional evidence for the source of Razak Formation from the Zagros imbricated zone.
